Subluxation: Causes, Risk Factors, and Prevention

What are the three causes of subluxation?

Subluxation, commonly understood in exercise science and mainstream medicine as a partial dislocation of a joint, typically arises from three primary categories of causes: acute traumatic injury, chronic joint instability often due to muscular imbalances or connective tissue laxity, and degenerative changes within the joint structure.

Understanding Subluxation in Biomechanics

In the realm of exercise science and biomechanics, a subluxation refers to a state where a joint's articular surfaces lose some contact, but not completely. Unlike a full dislocation (luxation), where the joint surfaces are entirely separated, a subluxation implies that the joint has moved beyond its normal anatomical limits but still maintains some degree of articulation. This partial displacement can lead to pain, instability, and impaired function. Understanding the root causes is crucial for prevention, rehabilitation, and effective management.

1. Traumatic Injury

Acute traumatic events are a leading cause of subluxation, particularly in highly mobile joints like the shoulder or patella. These injuries involve a sudden, forceful external stress that overwhelms the joint's inherent stability mechanisms.

• Direct Impact: A direct blow to a joint can force it partially out of alignment. For instance, a fall onto an outstretched arm can cause a shoulder subluxation, or a direct impact to the knee can lead to patellar subluxation.
• Excessive Force or Torque: Movements that involve sudden, extreme ranges of motion or powerful twisting forces can lead to subluxation. This might include:
  • Hyperextension or Hyperflexion: Forcing a joint beyond its normal limits (e.g., hyperextension of the elbow or knee).
  • Excessive Rotation: Sudden, uncontrolled twisting motions, such as pivoting rapidly during sports, can subluxate joints like the knee or ankle.
  • Strong Muscle Contractions Against Resistance: In some cases, an extremely powerful, uncoordinated muscle contraction can pull a joint partially out of place, such as quadriceps contraction pulling the patella laterally.

The mechanism here involves the sudden stretching or tearing of the joint capsule, ligaments, and sometimes surrounding tendons, which are the primary static and dynamic stabilizers of the joint.

2. Chronic Instability and Biomechanical Imbalance

Beyond acute trauma, subluxation can result from long-standing issues that compromise joint stability over time. These often involve a complex interplay of anatomical predispositions and functional deficits.

• Ligamentous Laxity or Hypermobility: Individuals with naturally "loose" ligaments (generalized joint hypermobility) or those whose ligaments have been chronically stretched due to repetitive microtrauma are predisposed to subluxation. This can be genetic (e.g., Ehlers-Danlos syndrome) or acquired. When ligaments are excessively pliable, they provide insufficient passive support, allowing the joint to move into abnormal positions.
• Muscular Imbalance or Weakness: The muscles surrounding a joint provide crucial dynamic stability. If these muscles are weak, fatigued, or imbalanced (e.g., one muscle group is significantly stronger or tighter than its antagonist), they may fail to adequately control joint movement, increasing the risk of subluxation.
  • Weak Stabilizers: For example, weakness in the rotator cuff muscles can lead to shoulder subluxation, or insufficient strength in the vastus medialis obliquus (VMO) can contribute to patellar subluxation.
  • Poor Neuromuscular Control: Even with adequate strength, a lack of proprioception (the body's awareness of its position in space) or poor neuromuscular coordination can lead to uncontrolled movements that stress the joint's limits.
• Repetitive Stress and Overuse: Sustained, repetitive movements, especially those involving end-range motion or high impact, can gradually stretch joint capsules and ligaments, leading to chronic instability and eventual subluxation. This is common in athletes involved in overhead sports or activities requiring frequent pivoting.

3. Degenerative Joint Changes

As joints age or undergo prolonged wear and tear, structural changes can occur that diminish their stability and congruity, making them more susceptible to subluxation.

• Osteoarthritis (OA): This degenerative joint disease involves the breakdown of articular cartilage, the smooth tissue covering the ends of bones. As cartilage erodes, the joint surfaces become irregular, reducing the joint's ability to glide smoothly and maintain proper alignment. Bone spurs (osteophytes) can also form, altering joint mechanics and potentially leading to instability or malalignment.
• Disc Degeneration (Spine): In the spine, the intervertebral discs cushion and stabilize the vertebrae. With age or injury, these discs can lose hydration and height, becoming less effective as shock absorbers and spacers. This disc degeneration can lead to increased stress on the facet joints and ligaments, potentially resulting in vertebral subluxation (spondylolisthesis being a more severe form where one vertebra slips forward on another).
• Inflammatory Arthritis: Conditions like Rheumatoid Arthritis (RA) cause chronic inflammation within the joint, leading to damage of the joint capsule, ligaments, cartilage, and bone. This destruction can result in significant joint laxity and progressive subluxation, particularly in the hands, feet, and the atlantoaxial joint in the neck.

These degenerative processes compromise the static and dynamic integrity of the joint, making it more vulnerable to displacement even with minimal stress.

Risk Factors for Subluxation

Several factors can increase an individual's susceptibility to subluxation:

• Previous History of Subluxation or Dislocation: Once a joint has been injured, it is often more prone to future episodes.
• Generalized Ligamentous Laxity: Inherited predisposition to "loose" joints.
• Muscle Weakness or Imbalance: Particularly in the muscles surrounding the vulnerable joint.
• Participation in High-Impact or Contact Sports: Increases exposure to traumatic forces.
• Repetitive Overhead Activities: Common in athletes (e.g., swimmers, baseball pitchers).
• Poor Posture or Ergonomics: Can lead to chronic stress on spinal or peripheral joints.
• Age: Increased risk of degenerative changes.
• Certain Medical Conditions: Such as Ehlers-Danlos syndrome, Marfan syndrome, or inflammatory arthropathies.

Prevention and Management Considerations

Preventing subluxation largely revolves around optimizing joint health and stability:

• Strength Training: Focus on strengthening the muscles that dynamically stabilize vulnerable joints, ensuring balanced development around the joint.
• Proprioceptive Training: Exercises that improve balance and joint position awareness help the body react quickly to destabilizing forces.
• Proper Technique: Adhering to correct form in exercise, sports, and daily activities minimizes undue stress on joints.
• Flexibility and Mobility: While important, care must be taken not to overstretch already hypermobile joints. Focus on maintaining functional range of motion without compromising stability.
• Injury Rehabilitation: Thoroughly completing rehabilitation protocols after any joint injury is crucial to restore full strength, stability, and neuromuscular control.
• Ergonomic Adjustments: Optimizing workspaces and daily movement patterns can reduce chronic stress on joints, particularly in the spine.

When to Seek Professional Help

If you suspect a subluxation or experience symptoms such as persistent joint pain, instability, recurrent "giving way" of a joint, or associated neurological symptoms like numbness or weakness, it is essential to consult a healthcare professional. An accurate diagnosis and appropriate intervention are critical for preventing further damage and ensuring optimal joint function.